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Due to the popularization of nuclear energy and the application of nuclear technology, there is an increasing demand for uranium resources. Extraction of uranium from seawater has become a hot topic. To achieve uranium capture, a three-dimensional carbon structure material (GO/ZIF-8@SA) with ionic stress elastic expansion consisting of graphene oxide, ZIF-8 and sodium alginate was developed. Surface morphological characteristics and elemental composition evaluation were determined by using SEM. The doping concentration of the elements in the synthesized products was measured by EDS. XRD, FT-IR and XPS confirmed the successful doping of ZIF-8. In seawater spiked with uranium, GO/ZIF-8@SA showed not only an ultra-high adsorption capacity of 1897 mg·g−1 for U(VI), but also a high selectivity. Interestingly, the volume of GO/ZIF-8@SA can be elastically expanded with the adsorption of U(VI). The expanded microspheres can be directly captured from the seawater by the mesh sieve. GO/ZIF-8@SA solves the problem of balancing adsorption capacity and selectivity in a complex seawater environment, which gives it great potential for application in seawater uranium extraction. [Display omitted] • The material is a swelling elastic ball of "plum pudding structure". • The swelling rate of the pellets is proportional to the amount of uranium adsorbed. • The material has high selectivity and large adsorption capacity in seawater. • Regulates filter mesh aperture to selectively capture balls adsorbed to saturation. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) and its composite membranes have exhibited great potential for application in water purification and desalination. This article reports that a novel graphene oxide membrane (GOM) of ~5 µm thickness was fabricated onto a nylon membrane by vacuum filtration and cross-linked by amino acids (L-alanine, L-phenylalanine, and serine). The GOM cross-linked by amino acids (GOM-A) exhibits excellent stability, high water flux, and high rejection to metal ions. The rejection coefficients to alkali and alkaline earth metal ions through GOM-A were over 94% and 96%, respectively. The rejection coefficients decreased with an increasing H+ concentration. Metal ions (K+, Ca2+, and Fe3+) can be inserted into GOM-A layers, which enlarges the interlayer spacing of GOM-A and neutralizes the electronegativity of the membrane, resulting in the decease in the rejection coefficients to metal ions. Meanwhile, GOM-A showed quite high antibacterial efficiency against E. coli. With the excellent performance as described above, GOM-A could be used to purify and desalt water. [ABSTRACT FROM AUTHOR]

The cation transport behavior of thermally treated reduced graphene oxide membranes (GOMs) is reported. The GOMs were reduced by heat treatment at 25, 80, and 120 °C and then characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, and X-ray photoelectron spectroscopy to determine oxygen group content, C/O ratio, and layer spacing. The permeation rates of various cations with different sizes and charge numbers through these membranes were measured to understand the effect of the cations on transport behavior. The results indicated that the cation transport through the membranes depended on the layer spacing of the membrane and ion size and charge. Cations of the same valence permeating through the same GOM could be differentiated by their hydration radius, whereas the same type of cation passing through different GOMs could be determined by the spacing of the GOM layers. The cation valence strongly affected permeation behavior. The GOM that was prepared at 120 °C exhibited a narrow layer spacing and high separation factors for Mg/Ca, Mg/Sr, K/Ca, and K/Fe. The cations moving through the membrane could insert into the membrane lamellas, which neutralized the negative charge of the membrane, enlarged the layer spacing of the GOMs, and affected cation permeation. [ABSTRACT FROM AUTHOR]

Uranium as a strategic and non-renewable resource has been paid close attention to its efficient recovery and reuse from uranium-containing wastewater. Here, a composite bead was prepared by functionalized graphene oxide and sodium alginate (L-Lys-GO/SA) with ion-stimuli responsiveness for achieving U(VI) adsorption. The L-Lys-GO/SA-60 composite beads can selectively adsorb U(VI) with the maximum adsorption capacity (q max) of 704.22 mg/g. Interestingly, the composite beads will swell under the stimulation of ions, which is more conducive to rapid solid-liquid separation and U(VI) recovery at low energy consumption. More importantly, the composite beads also exhibit high reusability of U(VI) adsorption with excellent life span of 80.11 % adsorption rate after 9 cycles, meaning that the composite beads and technology may be used in extraction and production for U(VI) from uranium-containing wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]